Our clients reported that Adobe Reader x was not loading PDF forms. Adobe Reader popups an error message saying that "File does not begin with '%PDF-" when the form was rendering in IE. We tested with different browser and the form loaded fine in Google Chrome and Firefox with Reader X, but NOT on IE. We also open the generated PDF in notepad and the PDF does have %PDF-1.3 as the first line, below.

Is this a known issue with IE and ReaderX? Is there any fix in place for this issue in the next Reader X update? This is an severe problem for us since we have thousands of clients accessing our PDF forms daily. Our PDF forms are dynamically generated and automatically displayed to clients to print out at the end of a transaction, so they can't just download the form.

I encountered this problem when I created a skydrive account, uploaded some pdf files then got the "File does not begin with '%PDF-' response when I tried to open the files online using IE 8. I was able to open them on my iPhone so tried using Firefox to navigate to the skydrive account and had no problem opening the PDF files when using Firefox browser.